I've been taking celexa since December. I am now on 30mg and I've had some rough times on it, especially around that~ time of the month (PMS and celexa don't seem to mix well at all for me), but generally, it has helped a ton more than not. I was prescribed it directly for PTSD and the depression and anxiety that comes along with it. I'm still trying to see if I should move up to 40mg.
I think since you've been taking it so long, you're becoming immune to it. Maybe you should talk to your doctor about exploring other options. Wishing the best for you.
<Edited - capitalised first word of sentences, and 'i'.>